First a short answer to Michael van Beuren, yes, generation are counted in that way I described, but you have also right, the grandfather + x th counts as you say. Just a misunderstanding from my side of what it concerned.
Second, Mark Lowes , marriages have and still are one economic agreement, without the trust to each other marriages do not work. Sometimes I get the feeling that people are describing animal in breeding season, not humans. It is not that common generally that people are unfaithful, the rate globally there the expected or named father of a child is not the one, concerns some few percent depending also much where in the world, but 1-2% lies near the truth.
When dealing with statistics, you must get clear about the fact that most fathers doing a paternity suit usually has reason to it so the numbers thus becomes remarkably high among those who are not fathers in that particular surveys, roughly one in four in the worst countries, but it is not representative. There is also the biological fact that men do have some killer sperms, the one who are in a regular relationship will likely kill of any remains of another mans leftover, the chance are thereby natural limited if it just happens occasionally that the woman are unfaithful.
Then the next thing, if we look back there was a high social stigma connected with women that were promiscuous and even further back it could cost them their life. The methods for abortions was also risky, a conclusion would be that if a woman got pregnant with another man,
it would commonly be by someone other close in the family, uncle, cousin, or as a result of a rape, in the first cases, the genetic lineage would in many cases be the same as if her husband was the father, if the relative where on his side, certainly worth to take into account for if example the husband was noted to be away during the time of conception, but nowadays test shows no discrepancies. But still, a bastard has certainly almost through the whole christian history right until our days suffered both scorn and derision.